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BMB428
Dr. Song Tan
Physical Chemistry with Biological Applications
Fall 2007
1
Problem Set 24: Enzyme Kinetics  the Basics
Due Dec 4, 2007
1.
Consider the following set of elementary steps for an enzyme catalyzed reaction:
E
+
S
E•S
k
1
k
1
E•S
E + P
k
2
Using the same techniques that we applied to deriving rate laws for chemical reactions, derive an
expression for d[P]/dt.
Your answer should contain the term
kk
k
−
+
12
1
which we will define as K
m
, the
MichaelisMenten constant.
2.
The equation that you derived in question 1 is not particularly useful since it (hopefully) has a term
with the free enzyme concentration, [E].
Since enzyme concentrations are typically VERY low during
steady state kinetics, it is difficult to determine what fraction of the enzyme has no substrate bound, E,
and what fraction is in the E•S form.
Fortunately, it is possible to eliminate the [E] term.
Use the
equation [E]
0
= [E] + [E•S] to derive a new equation for d[P]/dt.
[E]
0
is the total (initial) enzyme
concentration that is added to the reaction.
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 Fall '07
 TAN

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